TOPIC: compression check

I would like to check the compression on my 1971 65hp. The problem is I'm not really sure what I'm doing though. What would the step by step procedures be? Yes I do have a gauge to check the compression though I don't know how to use it The motor is just sitting on a stand at the moment.

I'll give you my procedure, and anyone/everyone else can throw theirs out there for ya too.
First - make sure your spark plug wires are marked so they go back in the right place. (Some motors have wire holders or numbered wires that simplify this, but it's best to check before you pull them all off!)
Second - remove all spark plugs. Note which cylinder they came out of, any good repair manual will give you a guide to "reading" the plugs to tell you what's been going on in that cylinder.
Third - screw the compression gauge (carefully, don't want to bugger up the threads!) into the first hole, making sure the gauge is reset to "0".
Fourth - I like to use a hand starter switch, or jump wire across the starter solenoid to engage the starter. (This way it doesn't energize the ignition system.) Spin the motor over at least three times to get an accurate reading.
Fifth - check and record the reading on that hole, reset the gauge, and move on (repeat) to the next cylinder.
Sixth - when all cylinders have been tested, I like to squirt a little oil into each cylinder and repeat the above procedure. If the readings increase it indicates worn rings.

Hope this helps, if anyone has a better way or corrections to mine, please feel free to let us know.

Here's the link to a tutorial on the subject you might like to watch too:
www.themarinedoctor.com/cgi-bin/YaBB.pl?num=1114482356
(Still "paying it forward", Chris!)

The "Snap On Tool" manual that came with my very old compression gauge says to make sure the butterflies (metering plates) in the carburators are in the wide open position as well as the choke butterflies and to crank (turn over) the enginge the same number of revolutions for each cylinder....4-5 if you use 4 revolutions for #1 cylinder use the same amount for #2 and so on but no more than 5 revolutions and and HOT (engine warmed up) is more accurate than a cold compression check. Oh almost forgot.....some of the ignitions on these engines require you to "ground" the spark plug wires so you don't damage the ignition system!
My 2 cents Pete

Thanks guys that was exactly the information I was looking for.

The 2 stroke engine has great big holes in the cylinders ( ports )

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therefor there is no need to open the throttle plates when doing a compression check !!!!--Crank till the gauge stops going up.

This might seem like common sense BUT make sure your fuel line is disconected .I had a guy bring me a motor to fix once . He was doing a compression test and left the fuel line on .While he was cranking it the Carbs dribbled fuel out and with his wires hanging . A spark caught the fuel .Checking the Compression on a warm Motor OK ..On Fire MMMMMM Not such a good idea ...L.O.L.

The professor is right on the money - crank the engine until the compression gauge stops climbing.
I always spray fogging oil into the cylinders before doing a compression test rather than risk spinning the beast with dry cylinder walls and rings thart might result in unwanted scoring.
Either killing the spark or controlling it is very important.
MarkS posted a lot of good information regarding this testing.
Thom